package WordCount;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import java.io.IOException;

public class WordCountApp {

    public static class MyMapper extends Mapper<LongWritable,Text,Text,LongWritable>{

        LongWritable one=new LongWritable(1);
        @Override
        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
            //接受到的每一行数据
            String line =value.toString();
            //按照指定的分隔符进行拆分
            String[] words = line.split(" ");

            for(String word:words)
            {
                //通过上下文把map的处理结果输出
                context.write(new Text(word),one);
            }
        }

    }

    public static class MyReducer extends Reducer<Text,LongWritable,Text,LongWritable>{
        @Override
        protected void reduce(Text key, Iterable<LongWritable> values, Context context) throws IOException, InterruptedException {

            long sum=0;
            for(LongWritable value:values){
                //求key出现的次数总和
                sum+=value.get();
            }

            //最终统计结果的输出
            context.write(key,new LongWritable(sum));
        }
    }

    public static void main(String[] args)throws Exception {
        //创建Configuration
        Configuration configuration=new Configuration();

        //创建job
        Job job =Job.getInstance(configuration,"wordcount");

        //创建job的处理类
        job.setJarByClass(WordCountApp.class);

        //设置作业处理的输入路径
        FileInputFormat.setInputPaths(job,new Path(args[0]));

        //设置map相关参数
        job.setMapperClass(MyMapper.class);
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(LongWritable.class);

        //设置reduce相关参数
        job.setReducerClass(MyReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(LongWritable.class);

        //设置作业处理的输出路径
        FileOutputFormat.setOutputPath(job,new Path(args[1]));

        System.exit(job.waitForCompletion(true)?0:1);
    }

}